Electrical translating device



June 12, 1928. 1,672,967

s. s. A. WATKINS v ELECTRICAL TRANSLA'IING DEVICE Filed 0ot.,l7, 1925 II 50 Wye/77W? Jfm/e JAM/m2 W A779 Patented June 12, 1928.

UNITED STATES 1,672,967 PATENT OFFICE- STANLEY S. A. WATKINS. OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N, Y., A CORPORATION OF NEW YORK.

ELECTRICAL TRANSLATING DEVICE.

Application filed October 17, 1923. Serial No. 669,021.

This invent-ion relates to electrical translating devices.

It is av well known characteristic of vibrating bodies such as diaphragms that when equal driving forces are applied to them at different frequencies, a greater response or amplitude of vibration will be produced at some frequency than at others. This frequency is usually known as the natural frequency of the diaphragm. The variation in response at different frequencies results in distortion. It has been found that by the application of damping to the vibrating body or diaphragm,.its natural frequency or natural period may be altered and the distortion over a given range of frequencies conse quently reduced or substantially eliminated. This invention applies a new damping agent to the vibrating parts of an oscillograph for the purpose of eliminating distortion.

An object of this invention is to produce undistorted reproductions of the wave forms of electric currents or electromotive forces.

Another object of the invention is to translate electrical variations into impulses perceptible to the senses and to cause these impulses to give a true representation of the electrical variations.

A further object of this invention is to alter the natural frequency of vibrating reeds driven in accordance with varying electric energy by applying air damping thereto.

A feature of this invention relates to a method of mounting a light reflecting element between two vibratory portions of an oscillograph in such manner that air damping may be applied and flexibility may be secured.-

Another feature of this invention relates to an 'oscillograph element arranged to utilize electrostatic force as means for actuating its vibratory elements.

A still further feature relates to an oscillograph. element utilizing-magnetic forces as a means for actuating its vibratory members and having means for adjusting the reluctance of its magnetic circuit.

The objects of the invention may be accomplished by arranging the vibrating portions of an oscillograph element which may comprise, two vibrating members or reeds as for example. diaphragms adjacent to two fixed plates. The vibrating members are so positioned with respect to the fixed plates that a very thin film of air remains therebetween. Additional means comprising a very small mirror is flexibly connected to the ad- ]acent edges of the vibrating diaphragm for causing deflections in a beam of light which may be reflected upon a sensitized film. Means also provided for exerting a drivlng force upon the vibratory elementsand this driving force is preferably applied in accordance with the variations of an electric current through the medium of an electrostatic or magnetic field.

The drawings to which reference is made in the detailed descri tion which follows are illustrative of embo iments and details of this invention as follows:

Fig. 1. a vertical section of an oscillograph element employing magnetic driving means.

Fig. 2, a plan view of the device of Fig. 1.

Fig. 3, a perspective view of a mirror mounting.

Fig. 4, an adjustable air gap. magnetically-driven oscillograph element.

Fig. 5. a plan view of the device of Fig. 4.

Fig. 6, an oscillograph with rectangular diaphragms and suspension mountin Fig. 7, a plan view of the device 0 Fig. 6.

Fig. 8, an electrostatically driven OSClllO- graph.

Fig. 9. a plan view of Fig. 8.

Fig. 10. a practical application of the oscillograph of this invention.

Throughout the various figures of the drawing like reference characters have been used to denote like members.

Referring to Figs. 1 to 3, two halves 10 and 11 of a split. circular diaphragm are arranged in the same plane and adjacent to an annular plate 12 whereby a thin film of air at 14 and 15 is maintained for the purpose ofdamping. Mounted upon the semi-circular diaphragms 10 and 11 is a mirror 16. The diaphragms 10 and 11 are, in this instance. preferably of magnetic material- The damping plate 12 may be of any desired material preferably nonmagnetic, for example. brass. Adjacent to the diaphragms 10 and 11 is placed a three-pole electromagnet 17. This magnet comprises a core 20 which is laminated or otherwise constructed so as to reduce energy losses therein, and windings 21, 22 and 23.

The diaphragms 10 and 11, the damping plate 12 and the magnet 17 are held in their proper positions in a case 26 having a screw cap 27. The case and cap are preferably made of insulating material. such as bakelite or hard rubber.

The energizing coils 21. 22 and 23 are wound upon the respective poles of magnet 17. The winding 22 which is on the middle pole is connected to a source of direct current 24 which causes the core to be normally polarized so that the middle pole has one polarity and the other two poles the opposite polarity.

' Windings 21 and 23 on the other respective poles of magnet 17 are connected preferably in series to a source of varying electromotive force or current 28 in such manner that when electric current flows therethrough, the magnetic field set up by one winding will aid the magnetic field of winding 22 and the field set up by the other winding will oppose the field of winding 22.

A mirror 16 flexibly attached to a pair of parallel wires or threads 30 and 31 in any well known manner. as. for example, by means of wax. mucilage. or gum. The wires supporting mirror 16 are soldered or otherwise attached to the two diaphragms 10 and 11.

Fig. 3 is a perspective view of another mounting for the mirror 16. The wires 30 and 31 are attached to posts 32 fixed to the diaphragms 10 and 11. The mirror is thereby raised above the diaphragms so that the gap between the diaphragms may be reduced. if desired.

In Fig. 1. when the source of varying electromotive force is connected at 28 as shown, the current in windings 21 and 23 is caused to vary and produce a corresponding variation in the magnetic field of core 20. Accordingly. the force exerted on diaphragms 10 and 11 produces vibration thereof. In order that the amplitude of this vibration shall be proportional to the amplitude of the current in windings 21 and 23. the thin film of air 15 is maintained adjacent to the diaphragms 10 and 11. This thin film of air is preferably given such dimensions as to providethe required damping action upon the vibrating parts. Since the windings 21 and 23 produce opposite poles. their action in causing deflection of diaphragms 10 and 11. will be in opposite senses; i. e., when the diaphragm 10 moves toward magnet 17, diaphragm 11 will move away from it. This motion of the diaphragms produces a deflection of mirror 16 which is proportional to the added deflection of both diaphragms.

Another form which the oscillographclement of this invention may take is shown in Figs. 4 and 5 wherein the central pole 35 of magnet 17 is adjustable by means of screw 36 acting in a slot 37. In this figure, the polarizing winding 22 is shown divided and positioned on the outer poles of the magnet 17. The damping plates 36 and 37 and the reeds or diaphragms 38 and 39 which are all rectangular in shape are attached to the core ofthe magnet 17 by means of screws.

The mirror 16 is mounted in the manner described in Fig. 2 between the rectangular vibratory reeds 38 and 39.

In the oscillograph of Fig. 6, two reotangular diaphragms 38 and 39 are suspended in front of the poles of magnet 17 upon parallel wires 40 and 42 and 41 and 43, respectively, lying in the same plane.

In the plan view shown in Fig. 7 the plates 36 and 37 are omitted to show the form of the mounting of the reeds 38 and 39 more clearly. Wires 40 and 41 are preferably rigid, whereas wires 42 and 43 are preferably resilient to allow vibration of the diaphragms about the wires 40 and 41 as axes. The mirror 16 is positioned between slots in the adjacent edges of diaphragms 38 and 39. It is attached to Wires 42 and 43 in the manner already described.

Figs. 8 and 9 illustrate a form of electrostatic oscillograph. The vibrating elements or diaphragms 10 and 11 are damped by the air films 14 and 15 maintained by the conducting plate 45. The diaphragms 10 and 11 are insulated from conducting plate 45 by an insulating washer 46. A mirror 16 is flexibly attached to the diaphragms 10 and 11 across the gap between them.

Diaphragms 10 and 11 are connected in parallel branches of an electric circuit including the secondary 47 of a transformer 48 differentially connected to one terminal of a battery 49. The opposite terminal of the battery connects to the conducting plate 45. A primary 50 of transformer 48 is connected to leads arranged to be connected to a source of varying electromot'ive force or current.

The electromotive force set 'up' in the sec.- ondary 47 by a ch'ange of current in the primary 56 produces a potential, difl'erence between the diaphragms 10 and 11 and the conducting plate 45 respectively one of which opposes that produced by batterv 49 and the other aids it. Thus one diaphragm is drawn from its normal position toward the plate 45 whereas the other diaphragm moves from its normal position in a directlon away from plate 45. Thus the movement of the. diaphragms in opposite directions is additive in deflecting mirror 16.

Fig. 9 which is a plan view of the device of Fig. 8-needs no additional explanation.

Referring to Fig. 10, block 51 represents a source of variable electromotive force or current, as, for example. a battery and transmitter. connected to the windings 21 and 23 of a. device such as shown in Fig. 1. The electric current produced by the device 51 effects the operation of oscillograph element 52 in the manner already described, whereby deflections of mirror 16 in accordance III therewith, are produced. A suitable source -59 preferably of monochromatic light is concentrated by a suitable lens system 60 into the parallel beam 61 and reflected by the mirror 16, upon the nttltHW slit 62. through which it passes to fall upon the film 63, which is sensitized with a suitable photographic emulsion. As the mirror is actu ated' in accordance with the variations of source 51. the beam of light is deflected so that a greater or lesser portion of it passes through the slit 62 to the film 63.

The motion of mirror 16 is such as to cause the reflected beam of light to move transversely with respect to the direction of longitudinal movement of the strip of photographic emulsion and to more in such manner that the beam of light. as a brush will cover onlv one-half of the width of the .strip when the light beam is stationarv. where-as, whenin transverse motion. the

light beam will cover more or less of he Width of the photographic emulsion by an amount proportional to the momentary current supplied to the distortionless translating. device 52. The photographic strip 63 is unwound from the reel 64. past the slit- 62. upon another reel 65. where it is' sto ed until its development. The width of the slit 62 thatis its dimension in the direction of motion of the film'is small as compared with the variations in the photographic records which are to be recorded and which correspond to the frequencies of the source 51., In other words. the width of the slit is made so narrow that the time required for" a given pointon the photographic emulsion to pass across the opening of the slitLis a small fraction of the time otthe cvcle of the maximum frequency of source 51. which is to be recorded. The strip 63 with its photographic emulsion. may consist of a strip of paper. celluloid or any other suitable material that may be found most 'convenient. I

It is not intended that the invention herein disclosed shall be limited to the specific embodiments described but. only .by the appended claims.

The invention claimed is:

1. In an oscillograph, in combination, a

pair ofmagnetic vibratory armatures, electromagnetic means responsive to current va-.

riations to be detected for deflecting the armatures in opposite directions, and a mirror adapted to be vibrated in accordance with cumulative movement ofthe armatitres.

2. In an osclllograph in combination, a.

pair of clamped magnetic armatures having vice of an electromagnet having a plurality of windings, means for energizing one of said windingsby'direct current, and means for connecting a source of electromotive force to be analyzed to another of said windingswhereby a magnetizing force opposing that produced by the winding energize-d with direct current is produced, a plurality of diaphragms adjacent to said electromagnet driven'in accordance-with variations in the resultant magnetizing force, and means adjacent to said diaphragms for producing athin film of air upon the surface thereof to equalize the response of said diaphragms to different frequencies.

4. In combination, a source of current, means for producing variations in the wave form of current. flowing from said source.

a pair of vibratory diaphragms actuated in opposite directions in accordance with the variations of the current. a mirror adapted to be moved in response to the cumulative movement of the diaphragms. and damping means for the diaphragms to prevent distortion of the wave form at frequencies corresponding to the natural frequencies of the diaphragms.

In witness whereof, I hereunto subscribe my name this 10th day of October A. D.,

STANLEY S. A. WATKINS. 

